External sizing of extensible paper

ABSTRACT

There is disclosed a method and apparatus for producing externally sized compacted paper which imparts to such paper radically improved stiffness, tensile, TEA and burst characteristics.

United States Patent 1191 Heim et a1.

[ Sept. 23, 1975 EXTERNAL SIZING OF EXTENSIBLE PAPER Inventors: Albert Heim, Wolleraw, Zurich,

Switzerland; Ernest J. Groome,

Covington, Va.

Assignee: Clupak, Inc., New York, NY.

Filed: Oct. 10, 1972 App]. No.: 295,919

U.S. Cl. 428/537; 162/100; 162/113; 162/175; 162/206; 427/211; 427/369; 427/326 Int. C1. B05C 9/04; B44D 1/092 Field of Search 117/60, 65.2, 68, 156;

References Cited UNITED STATES PATENTS 1/1953 9/1961 12/1966 [/1968 ll/l969 10/1970 Cluett 162/100 X Downs et 'al. 162/206 X Streb et al. 117/68 Welsh 162/175 Weber 117/68 Hoch 162/206 X Primary Examine r-Michael R. Lusignan ABSTRACT There is disclosed a method and apparatus for producing externally sized compacted paper which imparts to such paper radically improved stiffness, tensile, TEA and burst characteristics.

13 Claims, 9 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of8 3,908,071

FIG!

US Patent Sept. 23,1975 Sheet 2 0151 3,908,071

' US Patent Sept. 23,1975 Sheet 3 of 8 3,908,071

6 o M PA c TED v4mn CD TEAR UNCOMPACTED I I I I I I I I I I I I I I I I I I I I O O O STARCH (ECLIPSE N) FIG.4

US Patent Sept. 23,1975 Sheet 4 of8 3,908,071

CD TEAR (ems) COMPAQ TED \\\\vl|ll| UNCOMPACTED IB.6SR

2 4 v 6 8 IO STARCH US Patent Sept. 23,1975 Sheet 5 of8 3,908,071

MD TEAR (ems) L mesa 8O M 86 27.0 SR gzos g' SR 6O CQMPACTED \\\\'IIIII UNCOMPACTED 2 4 6 3 I'OV POTATO STARCH MD TEAR GMS 90 com: STARCH US Patent Sept. 23,1975 Sheet 6 of8 3,908,071

MD TENSILE (LBS/IN.)

COMPA CTED \\\\vllll 0 UNCOM PACTED '2 e3 5 \b POTATO STARCH i t 6 6 \b CORN STARCH (74,

FIG. 7

US Patent Sept. 23,1975 Sheet 7 of 8 3,908,071

MD STIFFNESS 270 SR llllll l8. 6 S R I Q I COM PAC TED \\\\Yllll UNCO MPACTED i 4 e a I I0 POTATO STARCH (7 MD STIFFNESS (TABoR) com: STARCH FIG. 8

EXTERNAL SIZING OF EXTENSIBLE PAPER BACKGROUND OF THE INVENTION Extensible (compacted) paper produced, for example, in accordance with the apparatus and process disclosed in US. Pat. No. 2,624,245 has certain well recognized advantages and commercial uses. Such paper is subjected, while in a partially moistened condition, to compressive compaction in the direction of web movement (machine direction or MD) between a pres sure nip, thus compacting and forcing the fibers together to produce an inherent stretchability without creping. Compacted paper has improved tensile energy absorption (TEA) burst and tear characteristics which are highly desirable for such end uses as the manufacture of paper sacks. However, extensible paper has reduced tensile strength and stiffness, the diminution of the latter characteristic increasing the difiiculty of converting this paper into sacks.

It is the purpose of the present invention to improve the tensile strength and stiffness of compacted paper without sacrificing tear strength and additionally, to produce a radical improvement in TEA and burst strengths. The method by which these objectives are achieved is by the selective impregnation of starch as an external sizing, particularly in a manner which will not destroy the extensible nature of the paper.

External sizing of non-extensible paper is well known and has generally been used to improve the printing qualities of higher grade papers by applying to one or both sides a coating of starch, clay, polyvinyl alcohol or the like. In a paper entitled On Machine Surface Sizing Trials With Acid Modified Wheat Flour Vol. 53 No. 8 August l970/Tappi, it was noted that the sizing of Kraft paper by applying thereto an acid-modified wheat flour or a hypechlorite-oxidized starch had the effect of increasing burst, tensile and stretch strengths. US. Pat, No. 3,362,869 to Welch discloses the application of a starch coating to one side of a moist compacted paper prior to drying of the paper in order to provide glazing thereof. It is the teaching of this patent that ordinary glazing of compacted paper by reintroducing sufficient moisture for this purpose into the web after compacting would destroy much of the extensible nature of the web and its attendant advantages. Therefore, in order to avoid undue wetting of the web, a coating of starch is applied to one surface of a still moist web after compacting and immediately prior to a drying roll, which inhibits increasing the moisture content of the web while the starch adhesively bonds the web to the drying roll and when the web is held under pres sure against the roll, results in glazing of the starch coated side of the web.

It is the purpose of the present invention to treat a compacted paper web with a starch solution in a particular way which overcomes or disregards the adverse effect upon the compacted web caused by introducing moisture thereto.

SUMMARY OF THE INVENTION In accordance with the present invention, it has been discovered that the controlled application of a water improvements it is possible to utilize some pulp stock (furnishes) previously thought to be totally unsuitable for the manufacture of paper for sacks, and alternatively makes possible the use of'less, conventional raw pulp stock without sacrificing strength.

As a further aspect of the invention a method for externally sizing compacted paper web has been devised wherein starch in solution, eg. potato, corn or wheat starch is impregnated under pressure into both sides of the web by percentage weight of l to 10% while moisture absorbed by the web is controlled such that after drying the web retains essentially all of the improved qualities afforded by compaction and is further improved in its tensile, burst, TEA and stiffness qualities. The stiffness imparted by such treatment produces compacted paper approximately as stiff as noncompacted paper (rendering such paper easily convertible into sacks) while the other enumerated strength qualities are drastically improved in comparison to compacted paper and of course non-compacted paper.

In accordance with the invention, it is intended that internal resin sizing may be used to control the degree of moisture absorption during the application of the starch solution to the web. Other techniques for selectively controlling moisture absorption may also be used, for example, the strength of the starch solution may be regulated in accordance with the elapsed time from the application of the starch solution to the web to the subsequent drying of the web.

As a further application of the above described principle, it is contemplated that relatively unrefined or unbeated paper fibers may be treated in accordance with the inventive method to produce a paper product having optimum or near optimum tensile and tear strengths. Unrefined paper fibers in a web exhibit relatively greater tear strengths and lesser tensile strengths than does a web produced from refined fibers. The impregnation of starch sizing as disclosed herein can produce a commensurate increase in tensile strength with respect to unrefined fiber webs, without substantial loss in tear strength.

Further aspects and objectives of the invention will be seen by examination of the following detailed specification, including specific examples, and accompanying drawings in which:

FIG. 1 is a schematic representation of a compactor for producing extensible paper,

FIG. 2 is a schematic representation of dryer sections which receive the compacted web after processing by the apparatus of FIG. 1 and a size press intermediate said dryer sections for applying a solution of starch into the web; and

FIG. 3 is a schematic illustration of an alternate form of the invention wherein the compacted web is fed directly to a size press and therefrom to a dryer section, and

FIGS. 49 illustrate graphically the effects of varying percentages of starch vis a vis different strength factors, compacted and uncompacted paper.

Referring now to the drawing, FIG. 1 illustrates generally a compactor 10 for producing an uncreped extensible paper web 11. The apparatus 10 includes a loopedelastomeric traveling belt 12, and a rotary cylin 'der 13 having a smooth (chrome plated) outer surface for receiving the web 11 thereon. A plurality of guide rolls l4, l5, l6 and 17 are positioned within the loop of the belt 12, guide roll 14 operating to squeeze the belt 12 against the cylinder 13 at a press nip N wherein the belt 12 is temporarily reduced in thickness as it travels therethrough. A section of the guide rolls 15 is spaced from the first guide roll 14 and urges a portion 12a of the belt against the cylinder 13 at the offrunning side of the nip N, and web guide means 18, 19 feed the web onto the cylinder 13 for movement through the nip N. The apparatus 10 is shown located in a paper machine between the second and third dryer sections. A dryer roll shown fragmentarily at 20 indicates the last roll of the second dryer section and the roll 33 (also shown fragmentarily) indicates the first roll of the third dryer section 30. The web is conveyed from the dryer roll 20 beneath the paper roll 19 and over an expander (paper guide) roll 18, and then into the nip N. The web 11 is brought into contact with the surface of the chrome plated roll 13 before it enters the nip N. The web 11 is then held against the surface of the roll 13 for an appreciable angular distance by the belt portion 12a and the web is then separated from both the belt 12 and the surface of the roll 13 and trained around a paper guide roll 22 and over another expander guide roll 23 and onto the dryer roll 33.

The web 11 coming off the dryer drum 20 has the optimum amount of moisture required for the compacting treatment. This optimum may vary between 20 to 50 percent moisture as the web 11 enters the apparatus 10.

As previously indicated, the roll 13 has a smooth surface, preferably chrome plated. The roll 13 is mounted on bearings 13a for rotation and is driven by a suitable source of power, such as a motor indicated diagrammatically at M. In fact, the motor M is the driving power for the entire device 10. In this way, the roll 13 drives the belt 12 primarily through pressure engagement at the nip N so that tension in the belt 12 is reduced at the nip N. As will be appreciated, some power is required to drive the belt 12 around the various guide rolls, such as the rolls 14, l5, l6 and 17 and the point at which the belt 12 is driven (which in this case is at the nip N) is a point at which tension in the belt is reduced. Since the belt is elastomeric in character there is a slight reduction in the stretching of the belt resulting from the reduction in tension and this causes the belt 12 to compress the web 11 longitudinally ofits direction of travel as the web 11 passes through the nip, and immediately thereafter. The smooth surface of the roll 13 is conducive to relative sliding between the web 11 and the roll 13. The web 11 which is held in close frictional contact with the belt is thus compacted in the machine direction (MD) without creping. A lubricant shower 25 is provided just beneath the web 11 at the oncoming side of the nip N. Preferably the lubricant shower 25 is a silicone shower but other release agents are suitable which applies a relatively small amount of liquid, in the form of a film, to the surface of the roll 13.

The roll 13 is heated, as shown here diagrammatically, by a suitable source of steam S fed axially into the roll 13 in the manner in which steam is fed into the usual paper machine dryer drum. The steam maintains a relatively high temperature about 212 and up to 350 F. at the surface of the roll 13 so as to create a very thin steam film or cushion between the web 11 and the drum 13. This steam cushion assists in permitting relative sliding between the web 11 and the drum 13 (which is essential to permit the web to be compacted by the belt) and tends to soften some of the ingredients of certain types of paper.

The apparatus thus far described is well known and forms no part of the present invention beyond illustrating the production of compacted paper which is subsequently treated according to the invention. The remainder of this specification will be devoted to specific aspects of the treating of compacted paper in accordance with the teachings and discoveries afforded by the invention.

After leaving the compacting apparatus 10, the web 11 will pass through the dryer section 30 which includes conventional drying rolls 31-36, the web 1 1 first passing over drying roll 33 thence to roll 34 etc. as shown. Felt dryer belts 37 and 38 are arranged upon guide rolls 39 and in contact with the respective dryer rolls 3l36 to assure the intimate engagement between the web 11 and the respective dryer rolls.

After leaving the compactor 10, the moisture contained in the web is approximately 35 to 45% moisture by weight. After passing through dryer section 30, the moisture content of the web 11 will be approximately 7 to 15 percent of moisture by weight.

Reference numeral 40 indicates a size press arrangement for treating the dried compacted web 1 l in accordance with the present invention. Web 11 first passes over guide rolls 41, 42 and therefrom proceeds between a nip formed by two counter-rotating size press rolls 43 and 44. Nozzles 46, 47 control the starch metering valves 48, 49 in conduit 50, 51 which permit a metered quantity of a starch solution 52 to flow into the nip between size press rolls 43, 44. Edge catch pans 53 collect the excess starch solution at each end of the nip. The starch solution is supplied from a starch solution supply tank 54 having therein an agitator 56, starch in solution being drawn from the tank 54 through conduit 57 to the pump 58 which supplies metering valves 48 and 49. A starch return pump 60 serviced by line 61 from catch pans 53 returns the starch solution via line 62 to the supply tank 54.

During the passage of web ll between the nip of press roll 43 and 44, a solution of starch is applied under pressure to both sides of the web in accordance with varying percentages indicated below by way of specific examples. The passage of the web 11 through the starch solution and between the rolls 43, 44 will be sufficient and will be so regulated as to the speed of application and the strength of the starch solution to permit and to cause impregnation of starch into both surfaces of the web 11 in accordance with a predetermined amount. The weight of starch impregnated and deposited in the web will be from 1 percent to 10 percent by weight to the total weight of the web after drying in order to achieve good results, with optimums of different strength characteristics being obtained by impregnating starch in accordance with the percentage shown in FIGS. 4-9. During this process the moisture content of the web will increase from the 7 to 15 percent value at the outlet of the dryer section 30 to a value of 35 to 45 percent. v

Following the application and impregnation of starch into both sections of the web 11 the web passes around guide roll 64 and thence into the second dryer section 66. Dryer section 66 contains a plurality of dryer rollers 67, 68, 69, 70, etc. about which pass dryer felts 71, 72 guided by rolls 73. The dryer section 66 is similar in all respects to the dryer section 30 and the web 11 passing therethrough will lose the moisture imparted by the size press existing from the dryer section 66 with moisture content of approximately 5 to percent by weight.

FIG. 3 discloses an alternate embodiment of the invention wherein the same reference numerals have been used for similar parts as shown in FIG. 2. In accordance with the embodiment of FIG. 3, the web 11 proceeds directly from the compactor 10 without first going through dryer section 30. As a consequence, the web 11 contains approximately 30 to 40 percent moisture by weight prior to passing between the size press rolls 43, 44. It willbe appreciated that since the web 11 contains this amount of moisture, lesser amounts of the starch solution will be caused to impregnate the web; however, a sufficient amount of starch in solution will impregnate the web to provide significant and beneficial results in regard to increasing tensile, burst and TEA characteristics, and may be expected to be in the order of approximately 50 percent of the improvement achieved with the configuration of FIG. 2. After passing through the size press 40, the web 11 feeds into the dryer section 66 which reduces the moisture content of the web to a moisture level of 5 to 10 percent by Weight. The advantage of the arrangement shown in section 3 is the use of asimgle dryer section to receive the web from the size press, although the moisture content of a web will ordinarily require a larger dryer sec tion to reduce the moisture content to acceptable levels.

It should be noted that with respect to both arrangements, FIGS. 2 and 3, it should be possible to obtain glazing of the paper web 11 by feeding the web downstream of the size press 40 around a single dryer roll provided that the starch solution when applied in the press 40 provides sufficient bonding of the web to the cylinder. In order to achieve glazing, a pressure contact with the drying cylinder, as shown for example in US. Pat. No. 3,362,869. The difference between the pressed arrangement and that shown in US. Pat. No. 3,362,869, referred to above in describing the background of the present invention, is that the starch applied in the said United States Patent is a surface coating used to achieve adhesive bonding between the web and the dryer roll, whereas in the present invention the web becomes impregnated with starch on both sides to achieve the subsequent additional improvements of radically increased tensile, burst and TEA strengths. Such additional effects are made possible by the use of the size press, which includes the size press rolls for forcing the starch solution into both web surfaces.

Having described the apparatus of the invention we will now set forth several examples illustrating the particular constituents used in carrying out the invention and the measured results. Example No. 1:

EXAMPLE I STARCH Add.)

Tensile (lbs/in.)

MD 6.0 14.0 CD 5.5 8.8

Elong. (9:)

-Continued STARCH Add.)

CD 1.3 2.3 2.8 TEA (ft.lbs./ft.)

CD 0.62 1.66 2.60 Tear (gms) MD 54.8 63.6 66.8

CD 61.6 76.5 88.8 Burst (psi) 5.4 17.7 23.7 Stiffness (Tabor Units) EXAMPLE 2 FURNISH of unbleached 30% Softwood unbleached Hardwood REFINED (14 Sec. Williams Freeness) STARCH Unmodified Potato Starch STARCH 0% 1.3% 3.0% 5.7% 10.7%

Tensile (lbs/in.) 7.9 12.8 14.0 15.1 15.5 Stretch 8.5 7.2 7.1 7.2 7.1

TEA (ft.lbs./ft. 5.4 7.5 8.2 8.9 8.9

Stiffness Tabor 0.56 1.02 1.15 1.20 1.33 Tear (gms) MD 69.7 83.1 88.8 88.1 84.6 CD 88.4 100.4 103.2 101.6 101.0 Burst (psi) 8.7 16.6 17.7 19.3 25.8

EXAMPLE 3 FURNISH of unbleached 30% Softwood unbleached 70% Hardwood REFINED (40 Sec. Williams Freeness) STARCH (Acid Modified Corn Starch) STARCH Add.)

From the above examples, it is apparent that two factors strongly influenced the results. These were (1) the degree of refining applied and (2) the amount or type of starch added. Corn starch promoted greater improvements in tensile strength and stiffness than potato starch under identical conditions. These were the properties it was desired to improve for better converting characteristics. Moreover, it was concluded that although tear strength on compacted paper was generally reduced by increasing refining and increased starch levels, the effect at freeness levels usually associated with sack production may not be great enough to offset the other advantages of sizing. Generally at between 3 and 4% added potato starch, properties levelled out, showing no marked changes beyond this additive level. Contrasted to this, with added corn starch, trends in properties continued beyond this point. No tackiness or brittleness was apparent in any of the samples tested up to about 8%. Above this, however, some brittleness was observed.

In keeping with the principles of the present invention, it is suggested that slightly converted (plasticized) starch should be superior to highly converted starches, particularly at high percentage levels of starch impregnation. Such plasticized starch should be highly compatible'with the extensible qualities of compacted paper. This is not, however, in any way to suggest that the use of unconverted starch is undesirable, since the examples disclosed herein were made using starch in the highly converted form.

Referring to FIG. 4, a diminution of tear occurs on compacted paper with increasing starch content at 525 CF. (23.7 Schopper Riegler). This work was done with an acid modified corn starch (Eclipse N) manufactured by A. E. Staley. With a lower level of refining,'i.e., at 730 C. F. (14.3 Schopper Riegler), tear strength is markedly increased with increased starch levels. At some intermediate level of refining then, one would expect to see small effects. That this is true can be seen in the more extensive work done on potato starch (see FIG. 5), where the effect of increased starch on tear is in fact rather small. The tear appears to approach some fixed value which is probably dependent on pulp variables.

Tear strength of unrefined paper increases with starch addition because of greater fiber bonding which results in greater forces required to pull fibers loose during tearing. On refined stock used in this study it is believed that optimum bonding for tear development has already been achieved by refining, so that additional bonding caused by the starch leads to increased shear failure of the fibers and reduced tear. The CD (Cross Direction, as opposed to Machine Direction, MD) tear results which are in all cases considerably better for compacted than for uncompacted papers can be explained by the fact that in CD tear, the failure must propagate across compacted fibers, and that compacted fibers with their lower modulus and higher elongation are more difficult to shear than uncompacted fibers. The initial increase in CD tear as starch is increased results from greater bonding and more difficulty in rupturing these bonds. Further increases in starch level however, leads to increased fiber modulus or stiffness, as well as further increases in bonding which favors fiber shear failure and reduced tear.

As is'normal for extensible paper,'MD tear was somewhat lower than the CD values The refined stock lost tear strength on adding starch as previously discussed (see FIG. 6).

Now to direct attention to properties improved by the addition of starch, that is, tensile, stiffness and TEA, on FIG. 7 are'shown MD tensile results for potato and corn starch at different levels. Two different refininglevels were explored in each instance. Notethat whereas tensile gains for potato starch occur during the first 3% addition, increased tensile with corn starch continues to higher additive levels. Also it may be observed that the addition of 3% starch to compacted paper brings the tensile up to the level of the untreated (uncompacted) sample. This may be understood by recalling that the molecular structure of corn starch, having a more linear orientation than potato starch, creates a film with higher tensile strength.

The use of corn starch at high levels (5%) doubled stiffness of compacted sheets, approaching the untreated (uncompacted) control. On FIG. 8 can be seen the results for potato starch also, where gains are not as dramatic, particularly at theintermediate refining levels normal to sack paper production. At 3% potato starch addition, the maximum benefit a pears to have been achieved, an approximately 40% increase in stiffness. 5

Another property increased by starch addition is the work to break in the machine direction (TEA) largely contributed to by the increased tensile (see FIG. 9). While a 30% increase is evident with corn starch, only about half this can be obtained with the same level of potato starch. The usual five to seven fold MD TEA increase over uncompacted paper is evident, whether starch treated or not.

No significant differences in burst strength occurred between compacted and non-compacted sheets with increased size addition. About 30 to 40% increase at the 3% level were obtained in either instance. This is expected since CD tensile and TEA properties which affect burst, are not markedly changed during the compaction process. The results of the burst test are thus dependent on the starch level.

It will be understood that the foregoing description has been of specific embodiments of the invention and is therefore representative. In order to understand the scope of the invention, reference should be made to the appended claims.

We claim:

1. A method for treating a compacted paper web to improve its tensile strength and stiffness while further improving its burst and TEA characteristics, compris ing the steps of: taking paper which is extensible by having been compacted without creping, thus'having improved burst, TEA and tear characteristics, and impregnating under pressure 'both sides of said web with a solution containing starch, while controlling the degree of moisture absorption from said solution by said web; and causing said web to be dried after impregnation with said starch solution; said web containing about Im 10% by weight starch.

2. The method of claim 1 wherein said web contains at least about 3% by weight of starch.

3. The method according to claim 1 wherein said paper is compacted and dried to have a moisture content generally no greater than,l5% by weight prior to the application of said starch solution thereto.

4. The method according to claim 3 wherein said paper contains internal resin sizing in an amount to selectively control the absorption of moisture from said starch solution. i i

5. The method according to claim 1 wherein said paper has a moisture content generally no greater than 40% prior to the application of said starch solution thereto.

6. The method according to claim 1 wherein said paper is relatively unrefined prior to compaction to provide an optimum level of tear strength, and tensile strength is improved toward an optimum by the impregnation of said starch.

7. The method according to claim 1 wherein said starch is in a plasticized, converted state.

8. The method of claim 2 wherein said web contains greater than 3% by weight starch and the starch is corn starch.

9. As a new product, an extensible paper web containing fibers which have been compacted without creping to provide improved stretch, tear, burst and TEA characteristics, said web further having impregnated under pressure into both surfaces thereof a predetermined amount of finely divided particles of starch to provide substantially increased tensile, TEA and stiffness properties, said web containing about 1 to 10% by weight of starch.

10. The product according to claim 9 wherein the starch is in a plasticized, converted state.

11. The product according to claim 9 wherein said 

1. A METHOD FOR TREATING A COMPACTED PAPER WEB TO IMPROVE ITS TENSILE STRENGTH AND STIFFNESS WHILE FURTHER IMPROVING ITS BURST AND TEA CHARACTERISTICS, COMPRISING THE STEPS OF: TAKING PAPER WHICH IS EXTENSIBLE BY HAVING BEEN COMPACTED WITHOUT CREPING, THUS HAVING IMPROVED BURST, TEA AND TEAR CHARACTERISTICS, AND IMPREGNATING UNDER PRESSURE BOTH SIDES OF SAID WEB WITH A SOLUTION CONTAINING STARCH, WHILE CONTROLLING THE DEGREE OF MOISTURE ABSORPTION FROM SAID SOLUTION BY SAID WEB, AND CAUSING WEB TO BE DRIED AFTER IMPREGNATION WITH SAID STARCH SOLUTION, SAID WEB CONTAINING ABOUT 1 TO 10% BY WEIGHT STARCH.
 2. The method of claim 1 wherein said web contains at least about 3% by weight of starch.
 3. The method according to claim 1 wherein said paper is compacted and dried to have a moisture content generally no greater than 15% by weight prior to the application of said starch solution thereto.
 4. The method according to claim 3 wherein said paper contains internal resin sizing in an amount to selectively control the absorption of moisture from said starch solution.
 5. The method according to claim 1 wherein said paper has a moisture content generally no greater than 40% prior to the application of said starch solution thereto.
 6. The method according to claim 1 wherein said paper is relatively unrefined prior to compaction to provide an optimum level of tear strength, and tensile strength is improved toward an optimum by the impregnation of said starch.
 7. The method according to claim 1 wherein said starch is in a plasticized, converted state.
 8. The method of claim 2 wherein said web contains greater than 3% by weight starch and the starch is corn starch.
 9. As a new product, an extensible paper web containing fibers which have been compacted without creping to provide improved stretch, tear, burst and TEA characteristics, said web further having impregnated under pressure into both surfaces thereof a predetermined amount of finely divided paRticles of starch to provide substantially increased tensile, TEA and stiffness properties, said web containing about 1 to 10% by weight of starch.
 10. The product according to claim 9 wherein the starch is in a plasticized, converted state.
 11. The product according to claim 9 wherein said tensile, TEA and stiffness properties are each increased at least 50% in comparison with similar compacted paper not having said starch impregnation.
 12. The product of claim 9 wherein said web contains at least about 3% by weight of starch.
 13. The product according to claim 12 wherein the percentage is greater than 3% and the starch is corn starch. 